Yersinia enterocolitica infection is a food born pathogen that causes severe intestinal inflammation. Recently a regulator was cloned, rovA, that does not cause severe intestinal inflammation. The rovA mutant does not induce IL-1alpha in response to Yersinia infection. The aim of this proposal is to determine which bacterial genes are responsible for this phenotype as well as identifying the host factors that the bacterial proteins interact with. The role of IL-1 in the mortality seen in the murine model will be investigated. The specific aims will be addressed by taking advantage of the genetic tractability of yersinia and the murine model. A screen for rovA regulated genes has been done. These genes will be screened for their ability to induce IL-1 in vivo. Inflammation will be assessed histologically. The host factors will be identify by producing blocking antibodies